This invention relates generally to an electrophotographic printing machine, and more particularly concerns an improved cleaning system for use therein.
In the process of electrophotographic printing, a photoconductive surface is uniformly charged. The charged photoconductive surface is then irradiated with a light image of an original document. The light image projected onto the charged photoconductive surface selectively dissipates the charge to record thereon an electrostatic latent image of the original document. During development, toner particles are electrostatically attracted to the latent image rendering it visible. Subsequently, the toner powder image is trans-ferred from the photoconductive surface to a sheet of support material. The powder image is permanently affixed to the sheet of support material forming a copy of the original document thereon. The foregoing process is described in greater detail in U.S. Pat. No. 2,287,691, issued to Carlson in 1942.
Generally, residual toner particles remain adhering to the photoconductive surface after the transfer of the toner powder image to the sheet of support material. Hereinbefore, it has been the practice to use an A.C. voltage for neutralizing the photoconductive surface followed by the cleaning thereof with a rotating brush. This operation permits removal of the majority of the residual toner particles from the photoconductive surface. A vacuum system is frequently associated with the rotating brush for collecting the residual toner particles. The brush is rotated at a high speed, thereby loosening and removing the residual toner particles from the photoconductive surface. These loosened particles are withdrawn by the vacuum system into the collection bag. Such an apparatus is an efficient structure for the removal of residual toner particles from the photoconductive surface. However, constructions of this type increase costs and complexity making it difficult to produce a compact copying apparatus. Moreover, systems of this type are frequently inefficient and may result in marginal cleaning, or filming of the photoconductive surface. The air flow is frequently applied as much as 270.degree. from the area to be cleaned. This can cause further brush contamination as the residual toner particles are being transported with the brush. In addition, air flow components exist in a radial direction toward the brush fiber roots. This prevents separation of the toner particles from the brush. Optimumly, the toner particles should be separated from the brush as soon as possible.
Accordingly, it is a primary object of the present invention to improve the cleaning apparatus of an electrophotographic printing machine.